聚羧酸系减水剂掺量和速凝剂掺加时段对无碱液体速凝剂作用效果的影响及机理  

Effect and Mechanism of Dosage of Polycarboxylate Based Plasticizer and Adding Period of Flash Set Admixture on the Effect of Alkali-free Liquid Flash Set Admixtures

作　　者：孙振平[1,2,6] 耿瑶 田俊涛 王宇峰 朱成桂 窦仁国 黄山 杨海静 李志林[4] 马跃飞 

机构地区：[1]同济大学先进土木工程材料教育部重点实验室,上海201804 [2]同济大学材料科学与工程学院,上海201804 [3]中铁上海工程局集团物资工贸有限公司,上海201906 [4]云南氟业环保科技股份有限公司,云南昆明313000 [5]乌兰浩特市圣益商砼有限公司,内蒙古乌兰浩特137400 [6]上海市水务局城市管网智能评估与修复工程技术研究中心,上海201900

出　　处：《混凝土世界》2023年第3期76-83,共8页China Concrete

基　　金：中铁上海工程局集团有限公司科技开发计划课题(SH-2020-重点-19);上海市科委项目(19DZ1201404,19DZ1202702);上海市科委外专项目(22WZ2502400);上海市建委项目(住建管2021-001-002);重庆市科技局专项项目(cstc2020kqjscx-phxm1594);内蒙古自治区科技计划项目(2022YFDZ0063);云南省科技厅专家工作站项目(202105AF150243)。

摘　　要：本文论述了喷射混凝土工程应用无碱液体速凝剂的重要性,并根据工程应用信息和课题组研究成果,对速凝剂的适应性做了定义,剖析了影响速凝剂应用效果的因素。利用所研制的无碱液体速凝剂AF-LR,以硫酸铝(Al_(2)SO_(4))为主要速凝组分,就聚羧酸系减水剂(PCE)掺量和速凝剂掺加时段对无碱液体速凝剂作用效果的影响及机理进行了试验研究。结果表明:掺加PCE会使AF-LR的速凝作用减弱,原因在于PCE虽可在一定程度上加快浆体水化早期钙矾石(AFt)的生成,但PCE自身具有的缓凝作用却会显著延长水泥水化反应的诱导期;在已拌合好的水泥浆体中,AF-LR掺加时间越晚,促凝效果越差。其原因在于,在没有速凝剂存在的情况下,水泥颗粒与水接触后,水泥水化反应完成诱导前期并进入相对“停滞”的诱导期,铝酸三钙(C_(3)A)的表面被已经形成的AFt紧密包裹,此时加入速凝剂,仅靠速凝剂引入的Al^(3+)和SO_(4)^(2-),难以形成足够多的AFt使水泥浆体快速凝结。This paper discusses the importance of the application of alkali-free liquid flash set admixtures in shotcrete engineering,defines the adaptability of alkali-free liquid flash set admixtures according to the engineering application information and research results of the research group,and analyzes the factors affecting the application effect of alkali-free liquid flash set admixtures.By using the developed alkali-free liquid flash set admixtures AFLR(in which Al_(2)SO_(4)is the main quick setting component),the influence of the dosage of polycarboxylate based plasticizer(PCE)and the adding period of flash set admixture on the effect of alkali-free liquid flash set admixture and its mechanism were studied experimentally.The results show that:1)The addition of PCE will weaken the rapid setting effect of AF-LR,because although PCE can accelerate the formation of ettringite(AFt)in the early stage of cement hydration to a certain extent,the retarding effect of PCE itself will significantly prolong the induction period of cement hydration reaction.2)In the mixed cement paste,the later the AF-LR is added,the worse the accelerating effect is.The reason is that,in the absence of flash set amixure,after the cement particles contact with water,the cement hydration reaction completes the early induction period and enters the induction period of relative"stagnation".The surface of tricalcium aluminate(C_(3)A)is tightly wrapped by the formed AFt.At this time,an alkali-free liquid flash set admixtures is added,relying only on the Al^(3+)and SO_(4)^(2-)introduced by the alkali free liquid flash set admixture itself,it is difficult to form enough AFt to make the cement paste set quickly.

关 键 词：无碱液体速凝剂 适应性 聚羧酸系减水剂 掺量 掺加时段 钙矾石 

分 类 号：TU528.042[建筑科学—建筑技术科学]